1. Field of the Invention
The present invention relates to a vehicle alternator, and more particularly to a structure for mounting a vehicle alternator to an engine.
2. Description of the Prior Art
The appearance of a vehicle alternator in the prior art is shown in FIG. 4 in which there is found a front bracket 1 with upper and lower flanges 2a, 2b projecting therefrom. Bosses 4a, 4b are formed in the lower flange 2a and a boss 4c is formed in the upper flange 2b. Each of the bosses 4a, 4b, 4c is respectively provided with attachment bores 3a, 3b, 3c extending in a direction at right angles to the axial direction of the alternator. The bolts inserted through these attachment bores 3a, 3b, 3c are screwed tightly to mount the vehicle alternator firmly to an engine. Reference numeral 5 denotes a stator partially fitted in the front and rear brackets 1 and 6 and held securely therebetween by means of the bolts 7. The flange 8 integrally formed on the rear bracket 6 is fastened by means of a bush 9 and a bolt 10 to the lower flange 2a which is protrudingly formed on the lower portion of the front bracket 1. Pulley 11, in combination with a belt, transmits rotation of the engine to the rotor rotatably supported inside the vehicle alternator.
In the prior art structure described above, the front bracket 1 and the rear bracket 6 are usually cast in a casting process and then the portions required to be accurate in dimension such as the aforesaid attachment bores 3a, 3b, 3c, and bosses 4a, 4b, 4c are adjusted by machining operations. However, casting the substantially long or thick articles is likely to cause problems such as blisters or inverted blisters (dimples) therein, and further, the machining process in different directions can result in lower efficiency.
In the prior art apparatus, particularly the lower flange 2a may be cast with blisters or inverted blisters if it has a long pitch or span between the attachment bores 3a and 3b. Furthermore, since the bores 3a, 3b, 3c and bosses 4a, 4b, 4c are machined in a direction at right angles to the alternator axis while other parts in the both brackets 1 and 6, such as the through-holes through which the bolts 7 are inserted and fitting portions into which the stator 5 is fitted, are machined in the axial direction, low machining efficiency results, and poor dimensional accuracy as well, due to the frequent chucking operations. Besides, the attachment bores 3a, 3b, 3c and bosses 4a, 4b, 4c are provided in the front bracket 1, and owing to this, if the corresponding pitch at the engine site is different from that of the alternator site, the front and rear brackets 1 and 6 must be manufactured in accordance with the corresponding mounting pitch at the engine side.
As described above, the prior art vehicle alternator has disadvantages such as remarkably reduced excitation intensity resulting from the occurrence of blisters or inverted blisters in its casting process, and variation in the center of the pulley due to the poor dimensional accuracy in its machining process, which is observed when the alternator is mounted to the engine and rotated. Another problem is that each time an alteration in the mounting pitch of the engine site is made, brackets to be used exclusively for each engine must be manufactured, causing an increase in the number of types of apparatus, and difficult standardization thereof.